Predicting Liver Allograft Discard: The Discard Risk Index

No Improvement in Intention-to-treat Survival and Increasing Liver Nonutilization Rate During the MELD Era

BACKGROUND

Although post liver transplant survival rates have significantly improved during the past 2-3 decades, the trend in intention-to-treat (ITT) survival (survival from waitlist addition) has not been well studied.

METHODS

We conducted a retrospective analysis of Scientific Registry of Transplant Recipients data to determine the trend in ITT survival in liver transplant candidates. Adult (age ≧ 18 y) patients who were on the waitlist between the time period of March 1, 2002, to December 31, 2019 (n = 200 816) and deceased liver donors that were registered between the same time period (n = 152 593) were analyzed.

RESULTS

We found a constant increase in posttransplant survival rates; however, the ITT survival rates showed no statistically significant improvement through the study period. We observed significant linear increase in waitlist dropout rates over time. We also observed linear increase in liver nonutilization rate in both entire cases and brain-dead cases. Donor risk index increased significantly over the years; however, it was mostly driven by increase in donation after circulatory death cases; without donation after circulatory death cases, donor risk index was stable throughout the 17 y we observed.

CONCLUSIONS

The reason of the increased liver nonutilization rate is unclear; however, it is possible that reluctance to use high-risk organ to maintain better posttransplant outcomes contributed to this increase, which also could have led to increase in waitlist dropout rates and no improvements in ITT survival. Further investigation is warranted on the increased nonutilization rates to improve over all contribution of liver transplant to patient care.

Effect of the opioid crisis on the liver transplantation donor pool: A national analysis

BACKGROUND

Over the last decade there has been a surge in overdose deaths due to the opioid crisis. We sought to characterize the temporal change in overdose donor (OD) use in liver transplantation (LT), as well as associated post-LT outcomes, relative to the COVID-19 era.

METHODS

LT candidates and donors listed between January 2016 and September 2022 were identified from the Scientific Registry of Transplant Recipients database. Trends in LT donors and changes related to OD were assessed pre- versus post-COVID-19 (February 2020).

RESULTS

Between 2016 and 2022, most counties in the United States experienced an increase in overdose-related deaths (n = 1284, 92.3%) with many counties (n = 458, 32.9%) having more than a doubling in drug overdose deaths. Concurrently, there was an 11.2% increase in overall donors, including a 41.7% increase in the number of donors who died from drug overdose. In pre-COVID-19 overdose was the 4th top mechanism of donor death, while in the post-COVID-19 era, overdose was the 2nd most common cause of donor death. OD was younger (OD: 35 yrs, IQR 29-43 vs. non-OD: 43 yrs, IQR 31-56), had lower body mass index (≥35 kg/cm2, OD: 31.2% vs. non-OD: 33.5%), and was more likely to be HCV+ (OD: 28.9% vs. non-OD: 5.4%) with lower total bilirubin (≥1.1 mg/dL, OD: 12.9% vs. non-OD: 20.1%) (all p < .001). Receipt of an OD was not associated with worse graft survival (HR .94, 95% CI .88-1.01, p = .09).

CONCLUSIONS

Opioid deaths markedly increased following the COVID-19 pandemic, substantially altering the LT donor pool in the United States.

Decreased Utilization Rate of Grafts for Liver Transplantation After Implementation of Acuity Circle-based Allocation

BACKGROUND

The allocation system for livers began using acuity circles (AC) in 2020. In this study, we sought to evaluate the impact of AC policy on the utilization rate for liver transplantation (LT).

METHODS

Using the US national registry data between 2018 and 2022, LTs were equally divided into 2 eras: pre-AC (before February 4, 2020) and post-AC (February 4, 2020, and after). Deceased potential liver donors were defined as deceased donors from whom at least 1 organ was procured.

RESULTS

The annual number of deceased potential liver donors increased post-AC (from 10 423 to 12 259), approaching equal to that of new waitlist registrations for LT (n = 12 801). Although the discard risk index of liver grafts was comparable between the pre- and post-AC eras, liver utilization rates in donation after brain death (DBD) and donation after circulatory death (DCD) donors were lower post-AC ( P  < 0.01; 79.8% versus 83.4% and 23.7% versus 26.0%, respectively). Recipient factors, ie, no recipient located, recipient determined unsuitable, or time constraints, were more likely to be reasons for nonutilization after implementation of the AC allocation system compared to the pre-AC era (20.0% versus 12.3% for DBD donors and 50.1% versus 40.8% for DCD donors). Among non-high-volume centers, centers with lower utilization of marginal DBD donors or DCD donors were more likely to decrease LT volume post-AC.

CONCLUSIONS

Although the number of deceased potential liver donors has increased, overall liver utilization among deceased donors has decreased in the post-AC era. To maximize the donor pool for LT, future efforts should target specific reasons for liver nonutilization.

Breaking distance barriers in liver transplantation: Risk factors and outcomes of long-distance liver grafts

BACKGROUND

Long-distance-traveling liver grafts in liver transplantation present challenges due to prolonged cold ischemic time and increased risk of ischemia-reperfusion injury. We identified long-distance-traveling liver graft donor and recipient characteristics and risk factors associated with long-distance-traveling liver graft use.

METHODS

We conducted a retrospective analysis of data from donor liver transplantation patients registered from 2014 to 2020 in the United Network for Organ Sharing registry database. Donor, recipient, and transplant factors of graft survival were compared between short-travel grafts and long-distance-traveling liver grafts (traveled >500 miles).

RESULTS

During the study period, 28,265 patients received a donation after brainstem death liver transplantation and 3,250 a donation after circulatory death liver transplantation. The long-distance-traveling liver graft rate was 6.2% in donation after brainstem death liver transplantation and 7.1% in donation after circulatory death liver transplantation. The 90-day graft survival rates were significantly worse for long-distance-traveling liver grafts (donation after brainstem death: 95.7% vs 94.5%, donation after circulatory death: 94.5% vs 93.9%). The 3-year graft survival rates were similar for long-distance-traveling liver grafts (donation after brainstem death: 85.5% vs 85.1%, donation after circulatory death: 81.0% vs 80.4%). Cubic spline regression analyses revealed that travel distance did not linearly worsen the prognosis of 3-year graft survival. On the other hand, younger donor age, lower donor body mass index, and shorter cold ischemic time mitigated the negative impact of 90-day graft survival in long-distance-traveling liver grafts.

CONCLUSION

The use of long-distance-traveling liver grafts negatively impacts 90-day graft survival but not 3-year graft survival. Moreover, long-distance-traveling liver grafts are more feasible with appropriate donor and recipient factors offsetting the extended cold ischemic time. Mechanical perfusion can improve long-distance-traveling liver graft use. Enhanced collaboration between organ procurement organizations and transplant centers and optimized transportation systems are essential for increasing long-distance-traveling liver graft use, ultimately expanding the donor pool.

The short and long-term prognostic influences of liver grafts with high bilirubin levels at the time of organ recovery

BACKGROUND

Donors with hyperbilirubinemia are often not utilized for liver transplantation (LT) due to concerns about potential liver dysfunction and graft survival. The potential to mitigate organ shortages using such donors remains unclear.

METHODS

This study analyzed adult deceased donor data from the United Network for Organ Sharing database (2002-2022). Hyperbilirubinemia was categorized as high total bilirubin (3.0-5.0 mg/dL) and very high bilirubin (≥5.0 mg/dL) in brain-dead donors. We assessed the impact of donor hyperbilirubinemia on 3-month and 3-year graft survival, comparing these outcomes to donors after circulatory death (DCD).

RESULTS

Of 138 622 donors, 3452 (2.5%) had high bilirubin and 1999 (1.4%) had very high bilirubin levels. Utilization rates for normal, high, and very high bilirubin groups were 73.5%, 56.4%, and 29.2%, respectively. No significant differences were found in 3-month and 3-year graft survival between groups. Donors with high bilirubin had superior 3-year graft survival compared to DCD (hazard ratio .83, p = .02). Factors associated with inferior short-term graft survival included recipient medical condition in intensive care unit (ICU) and longer cold ischemic time; factors associated with inferior long-term graft survival included older donor age, recipient medical condition in ICU, older recipient age, and longer cold ischemic time. Donors with ≥10% macrosteatosis in the very high bilirubin group were also associated with worse 3-year graft survival (p = .04).

DISCUSSION

The study suggests that despite many grafts with hyperbilirubinemia being non-utilized, acceptable post-LT outcomes can be achieved using donors with hyperbilirubinemia. Careful selection may increase utilization and expand the donor pool without negatively affecting graft outcome.

The Role of Donor Gamma-Glutamyl Transferase as a Risk Factor for Early Graft Function after Liver Transplantation

BACKGROUND

Growing interest has been recently reported in the potential detrimental role of donor gamma-glutamyl transferase (GGT) peak at the time of organ procurement regarding the risk of poor outcomes after liver transplantation (LT). However, the literature on this topic is scarce and controversial data exist on the mechanisms justifying such a correlation. This study aims to demonstrate the adverse effect of donor GGT in a large European LT cohort regarding 90-day post-transplant graft loss.

METHODS

This is a retrospective international study investigating 1335 adult patients receiving a first LT from January 2004 to September 2018 in four collaborative European centers.

RESULTS

Two different multivariable logistic regression models were constructed to evaluate the risk factors for 90-day post-transplant graft loss, introducing donor GGT as a continuous or dichotomous variable. In both models, donor GGT showed an independent role as a predictor of graft loss. In detail, the log-transformed continuous donor GGT value showed an odds ratio of 1.46 (95% CI = 1.03-2.07; p = 0.03). When the donor GGT peak value was dichotomized using a cut-off of 160 IU/L, the odds ratio was 1.90 (95% CI = 1.20-3.02; p = 0.006). When the graft-loss rates were investigated, significantly higher rates were reported in LT cases with donor GGT ≥160 IU/L. In detail, 90-day graft-loss rates were 23.2% vs. 13.9% in patients with high vs. low donor GGT, respectively (log-rank p = 0.004). Donor GGT was also added to scores conventionally used to predict outcomes (i.e., MELD, D-MELD, DRI, and BAR scores). In all cases, when the score was combined with the donor GGT, an improvement in the model accuracy was observed.

CONCLUSIONS

Donor GGT could represent a valuable marker for evaluating graft quality at transplantation. Donor GGT should be implemented in scores aimed at predicting post-transplant clinical outcomes. The exact mechanisms correlating GGT and poor LT outcomes should be better clarified and need prospective studies focused on this topic.

Japanese national survey on declined liver allografts from brain-dead donors: High decline rate but promising outcomes in allografts with moderate steatosis

Aim

Liver allografts from brain-dead donors, which were declined and were eventually not transplanted due to accompanying marginal factors, have never been surveyed in Japan. We surveyed the declined allografts and discussed the graft potential focusing on various marginal factors.

Methods

We collected data on brain-dead donors between 1999 and 2019 from the Japan Organ Transplant Network. We divided their liver allografts into declined (nontransplanted) and transplanted ones, and then characterized declined ones focusing on their timepoints of decline and accompanying marginal factors. For each marginal factor, we calculated the decline rate from the number of declined and transplanted allografts, and assessed the 1-year graft survival rate from transplanted allografts.

Results

A total of 571 liver allografts were divided into 84 (14.7%) declined and 487 (85.3%) transplanted ones. In the declined allografts, a majority was declined after laparotomy (n = 55, 65.5%), most of which had steatosis and/or fibrosis (n = 52). Out of the moderate steatotic (without F ≥ 2 fibrosis) allografts (n = 33), 21 were declined and 12 were transplanted, leading to a 63.6% decline rate. The latter 12 achieved a 92.9% 1-year graft survival rate after transplantation. Comparison of donor background showed no significant difference between the declined and transplanted allografts.

Conclusion

Pathological abnormalities of steatosis/fibrosis seem to be the most common donor factor leading to graft decline in Japan. Allografts with moderate steatosis were highly declined; however, transplanted ones achieved promising outcomes. This national survey highlights the potential utility of liver allografts with moderate steatosis.

Is Liver Transplant Justified at Any MELD Score?

BACKGROUND

Assessing the survival benefit of transplantation in patients with end-stage liver disease is critical in guiding the decision-making process for liver allocation. Previous studies established increased mortality risk for those transplanted below Model for End-Stage Liver Disease (MELD) 18 compared with candidates who remained on the waitlist; however, improved outcomes of liver transplantation and a changing landscape in the donor supply warrant re-evaluation of this idea.

METHODS

Using the United Network for Organ Sharing database, we analyzed 160 290 candidates who were waitlisted for liver transplantation within MELD cohorts. We compared patients who were transplanted in a MELD cohort with those listed but not transplanted in that listed MELD cohort with an intent-to-treat analysis.

RESULTS

Those transplanted at a MELD between 6 and 11 showed a 31% reduction in adjusted mortality (HR = 0.69 [95% confidence interval [CI], 0.66-0.75]; P < 0.001) compared with the intent-to-treat cohort in a Cox multivariate regression. This mortality benefit increased to a 37% adjusted reduction for those transplanted at MELD between 12 and 14 (HR = 0.63 [95% CI, 0.60-0.66]; P < 0.001) and a 46% adjusted reduction for those transplanted at a MELD between 15 and 17 (HR = 0.54 [95% CI, 0.52-0.57]; P < 0.001), effects that remained in sensitivity analyses excluding patients with hepatocellular carcinoma, encephalopathy, ascites, and variceal bleeds. A multivariate analysis of patients transplanted at MELD < 18 found younger age and cold ischemia time were protective, whereas older age, lower functional status, and socioeconomic factors increased mortality risk.

CONCLUSIONS

These findings challenge the current practice of deferring liver transplants below a particular MELD score by demonstrating survival benefits for most transplant patients at the lowest MELD scores and providing insight into who benefits within these subgroups.

DCD Hepatitis C Virus-positive Donor Livers Can Achieve Favorable Outcomes With Liver Transplantation and Are Underutilized

BACKGROUND

Hepatitis C virus (HCV)-positive donors (antibody-positive [Ab + ] or nucleic acid test positive [NAT + ] donors) have been underutilized. The aim of this study was to evaluate the utilization of livers from HCV-positive with donation after circulatory death (DCD) and to assess outcomes in recipients of these grafts.

METHODS

Data between 2015 and 2019 were obtained from the United Network for Organ Sharing database. The utilization rates and graft survival among 8455 DCD liver and nonliver donors and 2278 adult DCD liver transplantation (LT) recipients were reviewed on the basis of donor HCV Ab/NAT status.

RESULTS

The utilization of Ab + /NAT - donors <40 y and Ab + /NAT + donors ≥40 y was low than utilization of HCV-negative donors ( P  < 0.001). Multivariate analysis identified HCV status (odds ratio [OR], 1.62; 95% confidence interval [CI], 1.06-2.48 in Ab + /NAT - , and OR, 1.49; 95% CI, 1.09-2.05 in Ab + /NAT + ) as an independent predictor of nonutilization of liver grafts. The rate of significant liver fibrosis was comparable in Ab + /NAT - (3.5%; P  = 0.84) but was higher in Ab + /NAT + (8.7%; P  = 0.03) than that in Ab - /NAT - donors. Kaplan-Meier survival curves demonstrated comparable 3-y patient survival in recipients of HCV-positive grafts compared with recipients of HCV-negative grafts ( P  = 0.63; 85.6% in Ab - /NAT - , 80.4% in Ab + /NAT - , and 88.7% in Ab + /NAT + ).

CONCLUSIONS

Patient and graft survival rates are similar between HCV-positive and HCV-negative DCD LT. However, HCV-positive donors are particularly underutilized for DCD LT.

Assessing Donor Liver Quality and Restoring Graft Function in the Era of Extended Criteria Donors

Liver transplantation (LT) is the final treatment option for patients with end-stage liver disease. The increasing donor shortage results in the wide usage of grafts from extended criteria donors across the world. Using such grafts is associated with the elevated incidences of post-transplant complications including initial nonfunction and ischemic biliary tract diseases, which significantly reduce recipient survival. Although several clinical factors have been demonstrated to impact donor liver quality, accurate, comprehensive, and effective assessment systems to guide decision-making for organ usage, restoration or discard are lacking. In addition, the development of biochemical technologies and bioinformatic analysis in recent years helps us better understand graft injury during the perioperative period and find potential ways to restore graft function. Moreover, such advances reveal the molecular profiles of grafts or perfusate that are susceptible to poor graft function and provide insight into finding novel biomarkers for graft quality assessment. Focusing on donors and grafts, we updated potential biomarkers in donor blood, liver tissue, or perfusates that predict graft quality following LT, and summarized strategies for restoring graft function in the era of extended criteria donors. In this review, we also discuss the advantages and drawbacks of these potential biomarkers and offer suggestions for future research.

Changing liver utilization and discard rates in clinical transplantation in the ex-vivo machine preservation era

Liver transplantation is a well-established treatment for many with end-stage liver disease. Unfortunately, the increasing organ demand has surpassed the donor supply, and approximately 30% of patients die while waiting for a suitable liver. Clinicians are often forced to consider livers of inferior quality to increase organ donation rates, but ultimately, many of those organs end up being discarded. Extensive testing in experimental animals and humans has shown that ex-vivo machine preservation allows for a more objective characterization of the graft outside the body, with particular benefit for suboptimal organs. This review focuses on the history of the implementation of ex-vivo liver machine preservation and how its enactment may modify our current concept of organ acceptability. We provide a brief overview of the major drivers of organ discard (age, ischemia time, steatosis, etc.) and how this technology may ultimately revert such a trend. We also discuss future directions for this technology, including the identification of new markers of injury and repair and the opportunity for other ex-vivo regenerative therapies. Finally, we discuss the value of this technology, considering current and future donor characteristics in the North American population that may result in a significant organ discard.

Salvage of Declined Extended Criteria DCD Livers Using in-situ Normothermic Regional Perfusion

OBJECTIVE

This study investigates whether liver grafts donated after circulatory death (DCD) that are declined by the entire Euro-transplant region can be salvaged with abdominal normothermic regional perfusion (aNRP).

SUMMARY BACKGROUND DATA

aNRP is increasingly used for DCD liver grafts because it prevents typical complications. However, it is unclear whether aNRP is capable to rescue pre-transplant declined liver grafts, by providing the opportunity to test function during donation.

METHODS

Donor livers from DCD donors, declined by all centers in the Euro-transplant region, were included for this study. The comparator cohort included standard DCD livers and livers donated after brain death, transplanted in the same time period.

RESULTS

After withdrawal of life-sustaining treatment, 28 from the 43 donors had a circulatory death within 2 hours, in which case aNRP was initiated. Out of these 28 cases, in 3 cases perfusion problems occurred, 5 grafts were declined based on liver assessment, and 20 liver grafts were transplanted. The main differences during aNRP between the transplanted grafts and the assessed non-transplanted grafts were ALT levels of 53 (34-68) versus 367 (318-488; P=0.001) U/l and bile production in 100% versus 50% of the grafts (P=0.024). The 12-month graft and patient survival were both 95%, similar to the comparator cohort. The incidence of ischemic cholangiopathy was 11%, which was lower than in the standard DCD cohort (18%).

CONCLUSIONS

aNRP can safely select and thus is able to rescue DCD liver grafts that were deemed unsuitable for transplantation, while preventing primary non-function and minimizing ischemic cholangiopathy.

Proposal and validation of a liver graft discard score for liver transplantation from deceased donors: a multicenter Italian study

Several studies have explored the risk of graft dysfunction after liver transplantation (LT) in recent years. Conversely, risk factors for graft discard before or at procurement have poorly been investigated. The study aimed at identifying a score to predict the risk of liver-related graft discard before transplantation. Secondary aims were to test the score for prediction of biopsy-related negative features and post-LT early graft loss. A total of 4207 donors evaluated during the period January 2004–Decemeber 2018 were retrospectively analyzed. The group was split into a training set (n = 3,156; 75.0%) and a validation set (n = 1,051; 25.0%). The Donor Rejected Organ Pre-transplantation (DROP) Score was proposed: − 2.68 + (2.14 if Regional Share) + (0.03*age) + (0.04*weight)-(0.03*height) + (0.29 if diabetes) + (1.65 if anti-HCV-positive) + (0.27 if HBV core) − (0.69 if hypotension) + (0.09*creatinine) + (0.38*log10AST) + (0.34*log10ALT) + (0.06*total bilirubin). At validation, the DROP Score showed the best AUCs for the prediction of liver-related graft discard (0.82; p < 0.001) and macrovesicular steatosis ≥ 30% (0.71; p < 0.001). Patients exceeding the DROP 90th centile had the worse post-LT results (3-month graft loss: 82.8%; log-rank P = 0.024).The DROP score represents a valuable tool to predict the risk of liver function-related graft discard, steatosis, and early post-LT graft survival rates. Studies focused on the validation of this score in other geographical settings are required.

Marginal allografts in liver transplantation have a limited impact on length of stay

The study of marginal liver transplant outcomes, including post-transplant length of stay (LOS), is necessary for determining the practicality of their use. 50 155 patients who received transplants from 2012 to 2020 were retrospectively analyzed with data from the Scientific Registry of Transplant Recipients database using Kaplan-Meier survival curves and multivariable Cox regression. Six different definitions were used to classify an allograft as being marginal: 90^th percentile Donor Risk Index (DRI) allografts, donation after cardiac death (DCD) donors, national share donors, donors over 70, donors with > 30% macrovesicular steatosis, or 90^th percentile Discard Risk Index donors. 24% (n = 12 124) of subjects received marginal allografts. Average LOS was 15.6 days among those who received standard allografts. Among those who received marginal allografts, LOS was found to be highest in those who received 90^th percentile DRI allografts at 15.6 days, and lowest in those who received DCD allografts at 12.7 days. Apart from fatty livers (95% CI .86-.98), marginal allografts were not associated with a prolonged LOS. We conclude that accounting for experience and recipient matching, transplant centers may be more aggressive in their use of extended criteria donors with limited fear of increasing LOS and its associated costs.

Development of the Eurotransplant Discard Risk Index to Predict Acceptance of Livers for Transplantation: A Retrospective Database Analysis

OBJECTIVES

The utilization of liver allografts could be optimized if nonacceptance is predicted. This study aimed to evaluate the prognostic ability of an updated Discard Risk Index in Eurotransplant.

MATERIALS AND METHODS

Potential deceased donors from January 2010 to December 2015 who had been reported to Eurotransplant were included in our analyses. Liver utilization was defined by transplant status as the primary outcome to evaluate the performance of the Eurotransplant-developed Discard Risk Index.

RESULTS

Of 11670 potential livers, 9565 (81%) were actually transplanted. Donor sex, age, history of diabetes, drug abuse, use of vasopressors, body mass index category, serum sodium, cause of death, donor type, and levels of C-reactive protein, bilirubin, aspartate and alanine aminotransferases, international normalized ratio, and gamma-glutamyltranspeptidase were associated with discard and combined in the Eurotransplant-developed Discard Risk Index. Correlation between the two Discard Risk Indexes was high (r = 0.86), and both achieved high C statistics of 0.72 and 0.75 (P < .001), respectively. Despite strong calibration, discard rates of 0.8% for overall donors and 6% of donors after circulatory death could be predicted with 80% accuracy.

CONCLUSIONS

The Eurotransplant-developed Discard Risk Index showed a high prognostic ability to predict liver utilization in a European setting. The model could therefore be valuable for identifying livers at high risk of not being transplanted in an early stage. These organs might profit the most from modified allocation strategies or advanced preservation techniques.

Ischaemia-free liver transplantation in humans: a first-in-human trial

Background Ischaemia-reperfusion injury is considered an inevitable component of organ transplantation, compromising organ quality and outcomes. Although several treatments have been proposed, none has avoided graft ischaemia and its detrimental consequences. Methods Ischaemia-free liver transplantation (IFLT) comprises surgical techniques enabling continuous oxygenated blood supply to the liver of brain-dead donor during procurement, preservation, and implantation using normothermic machine perfusion technology. In this non-randomised study, 38 donor livers were transplanted using IFLT and compared to 130 conventional liver transplants (CLT). Findings Two recipients (5•3%) in the IFLT group experienced early allograft dysfunction, compared to 50•0% in patients receiving conventional transplants (absolute risk difference, 44•8%; 95% confidence interval, 33•6-55•9%). Recipients of IFLT had significantly reduced median (IQR) peak aspartate aminotransferase levels within the first week compared to CLT recipients (365, 238-697 vs 1445, 791-3244 U/L, p<0•001); likewise, median total bilirubin levels on day 7 were significantly lower (2•34, 1•39-4•09 mg/dL) in the IFLT group than in the CLT group (5•10, 1•90-11•65 mg/dL) (p<0•001). Moreover, IFLT recipients had a shorter median intensive care unit stay (1•48, 0•75-2•00 vs 1•81, 1•00-4•58 days, p=0•006). Both one-month recipient (97•4% vs 90•8%, p=0•302) and graft survival (97.4% vs 90•0%, p=0•195) were better for IFLT than CLT, albeit differences were not statistically significant. Subgroup analysis showed that the extended criteria donor livers transplanted using the IFLT technique yielded faster post-transplant recovery than did the standard criteria donor livers transplanted using the conventional approach. Interpretation IFLT provides a novel approach that may improve outcomes, and allow the successful utilisation of extended criteria livers. Funding This study was funded by National Natural Science Foundation of China, Guangdong Provincial Key Laboratory Construction Projection on Organ Donation and Transplant Immunology, and Guangdong Provincial international Cooperation Base of Science and Technology. Panel: Research in context.

Machine Learning Prediction of Liver Allograft Utilization From Deceased Organ Donors Using the National Donor Management Goals Registry

Early prediction of whether a liver allograft will be utilized for transplantation may allow better resource deployment during donor management and improve organ allocation. The national donor management goals (DMG) registry contains critical care data collected during donor management. We developed a machine learning model to predict transplantation of a liver graft based on data from the DMG registry.

Methods

Several machine learning classifiers were trained to predict transplantation of a liver graft. We utilized 127 variables available in the DMG dataset. We included data from potential deceased organ donors between April 2012 and January 2019. The outcome was defined as liver recovery for transplantation in the operating room. The prediction was made based on data available 12-18 h after the time of authorization for transplantation. The data were randomly separated into training (60%), validation (20%), and test sets (20%). We compared the performance of our models to the Liver Discard Risk Index.

Results

Of 13 629 donors in the dataset, 9255 (68%) livers were recovered and transplanted, 1519 recovered but used for research or discarded, 2855 were not recovered. The optimized gradient boosting machine classifier achieved an area under the curve of the receiver operator characteristic of 0.84 on the test set, outperforming all other classifiers.

Conclusions

This model predicts successful liver recovery for transplantation in the operating room, using data available early during donor management. It performs favorably when compared to existing models. It may provide real-time decision support during organ donor management and transplant logistics.

Pediatric discard risk index for predicting pediatric liver allograft discard

BACKGROUND

Of the 600 pediatric candidates added to the liver waiting list annually, 100 will remain waiting while over 100 liver allografts are discarded, often for subjective reasons.

METHODS

We created a risk index to predict discard to better optimize donor supply. We used the UNOS database to retrospectively analyze 17 367 deceased donors (≤18 years old) through univariate and multivariate logistic regression models. Deceased donor clinical characteristics and laboratory values were independent variables with discard being the dependent variable in the analysis. Significant univariate factors (P-value < .05) comprised the multivariate analysis. Significant variables from the multivariate analysis were incorporated into the pDSRI, producing a risk score for discard.

RESULTS

From 17 potential factors, 11 were identified as significant predictors (P < .05) of pediatric liver allograft discard. The most significant risk factors were as follows: DCD; total bilirubin >10 mg/dL, and alanine transaminase (ALT) ≥500 IU/L. The pDSRI has a C-statistic of 0.846 for the training set and 0.840 for the validation set.

CONCLUSION

The pDSRI uses 11 significant risk factors, including elevated liver function tests, donor demographics, and donor risk/type to accurately predict risk of pediatric liver allograft discard and serve as a tool that may maximize donor yield.

Allograft discard risk index for heart transplantation

BACKGROUND

The numberof patients awaiting heart transplantation (HTx) substantially exceeds the number of donor hearts transplanted each year, yet nearly 65% of eligible donor hearts are discarded rather than transplanted.

METHODS

Deceased organ donors listed within the UNOS Deceased Donor Database between 2010 and 2020 were reviewed. Those greater than 10 years old and consented for heart donation were included and randomly separated into training (n = 48 435) and validation (n = 24 217) cohorts. A discard risk index (DSRI) was created using the results of univariable and multivariable analyses. Discard data were assessed at DSRI value deciles, and stratum-specific likelihood ratio (SSLR) analysis and Kaplan-Meier survival function were used for mortality data.

RESULTS

Factors associated with higher DSRI values included donor age > 45, LVEF, HBV-core antibodies, hypertension, and diabetes. The DSRI C-statistic was .906 in the training cohort and .904 in the validation cohort. The DSRI did not reliably predict 30-day or 1-year mortality after transplantation (C-statistic .539 and .532, respectively).

CONCLUSIONS

The factors leading to heart allograft discard are not correlated to the same degree with post-transplant outcomes. This suggests that optimizing utilization of certain allografts with slightly higher risk of discard could increase the heart donor pool with limited impact on posttransplant mortality.

Intent-to-treat survival in liver transplantation has not improved in 3 decades due to donor shortage relative to waitlist growth

BACKGROUND

Liver Transplantation has advanced over the past 3 decades, with 1-year survival rates improving 25%. Survival rates for those transplanted has increased to remarkable levels, but survival from the time of listing may not be as revolutionary.

METHODS

Kaplan-Meier with log-rank test as well as Cox regression analysis was used to retrospectively analyze 211 610 adults listed for LT and 116 299 adult transplant recipients from 1987 to 2016. Our primary endpoints were survival from time of listing to waitlist death or posttransplant death.

RESULTS

One-year survival following LT improved dramatically (68% in 1987-1988 vs. 93% in 2016, P < .001). There was no improvement in 1-year intent-to-treat survival: 78.4% for those listed in 1987 and 81.8% for those listed in 2016 (P = .1). Also observed were decreases in the percentage of transplanted candidates from 74.8% in 1987-1988 to 54.7% in 2016 (P < .001) and increased 1-year wait-list mortality from 12.5% in 1987-1988 to 22.6% in 2016 (P = .002).

CONCLUSION

As transplant rate has decreased while waitlist mortality has increased, no improvements have been made in intent-to-treat survival of patients listed for transplant over the past 3 decades. We speculate this observation to be resultant of a relative donor shortage outpaced by waitlist growth.

SUMMARY

Liver Transplantation has experienced vast increases in survival rates over the past 3 decades; however, due to an increased donor supply outpaced by waitlist growth, the rate of transplantation has decreased significantly while the waitlist mortality has increased, leading to no improvement in 1-year intent-to-treat survival rates.

The prognostic significance of serum aspartate transaminase and gamma-glutamyl transferase in liver deceased donors

The impact of aspartate transaminases (AST) and gamma-glutamyl transferase (GGT) in serum of deceased donors on outcomes after liver transplantation (LT) is unclear. This study aimed to explore the relationship between donor highest AST value or first donor GGT value and graft survival. All consecutive patients who underwent a primary LT in a single center with available donor AST (N=1253) and GGT value (N=1152) were included. There was no significant association between donor AST and 90-day graft survival. We found a moderate association between GGT and 90-day graft survival. We found a significant interaction with a donor history of alcohol abuse (HAA). The risk of graft loss was associated with AST and GGT in donors with an HAA but remains unchanged in donors without HAA. There was no difference in graft survival according to donor AST or GGT with a cutoff ≥ 95^th percentile (475 UI/L for AST and 170 UI/L for GGT). However, graft survival was significantly decreased when donors combined GGT ≥ 170 UI/L and HAA (61% at one year). Hepatic grafts from donors with high AST or high GGT but without alcohol history and no additional risk factors can be transplanted in low-risk recipient.

Doppler ultrasonography and contrast-enhanced ultrasonography to evaluate liver allograft discard: A pilot prospective study

BACKGROUND

Broad hemodynamic changes, is believed to have a profoundly damaging effect on donor livers after brain death (DBD) or cardiac death (DCD). It remains unclear whether Doppler ultrasonography (DUS) and contrast-enhanced ultrasonography (CEUS), the imaging modalities to evaluate perfusion, could provide more information of liver discarded.

OBJECTIVE

To evaluate the ability of DUS and CEUS to predict the risk of DBD or DCD liver discarded.

METHODS

The consecutive DBD or DCD donors with DUS/CEUS examinations before surgical procurement from February 2016 to June 2018 at our institution were included. The US and CEUS images of each donor liver were analyzed and the parameters were recorded.

RESULTS

Among the 67 eligible donor livers, 15 (22.4%) were discarded and 52 (77.6%) were used. The discarded livers showed prolonged SAT of hepatic artery (0.08s vs 0.06s, OR = 2.169, P = 0.008) on DUS, less cases with homogeneous enhancement (40.0% vs 73.1%, OR = 0.243, P = 0.028) on CEUS, more cases with decreased enhancement (53.3% vs 19.2%, OR = 4.800, P = 0.009), and less difference of the peak time between portal vein and liver parenchymal (0.5s vs 6.7s, OR = 0.917, P = 0.034). The multivariable analysis showed that donor liver with prolonged SAT of hepatic artery (OR = 7.304, 95% CI: 1.195-44.655, P = 0.031) and decreased enhancement (OR = 2.588, 95% CI: 1.234-5.426, P = 0.012) were independent factors of liver discarded.

CONCLUSIONS

DUS/CEUS could be applied as a promising predictive tool to screen high-risk liver donors. The prolonged SAT of hepatic artery on DUS and the decrease of liver donor in enhancement on CEUS, indicating hemodynamic changes in DBD and DCD donor livers, were risk factors of liver discarded.

Donor Gamma-Glutamyl Transferase Is Associated With Liver Allograft Discard and Failure

INTRODUCTION

The disparity between the number of individuals on the wait list and available liver allografts creates the need for a system that maximizes donor liver utilization and predicts graft failure.

RESEARCH QUESTION

This study aimed to determine the relationship between donor Gamma-Glutamyl Transferase (GGT), liver discard, and graft failure.

DESIGN

Through multivariate analysis from 53 966 deceased liver donors, we adjusted for donor clinical and demographic characteristics and compared donor GGT with allograft discard. We compared donor GGT ranges with graft failure and analyzed data from 47 269 liver recipients.

RESULTS

After adjusting for other factors, donor GGT was significantly associated with liver discard, with GGT over 200 U/L being most significant (OR 2.74, CI 2.51-2.99). Donor GGT under 20 U/L was also found to be a protective factor for post-transplant graft failure (HR 0.91, CI 0.83 - 1.00).

CONCLUSION

Going forward, GGT should be included among other characteristics associated with allograft discard considered during the procurement process.

Understanding the Final Disposition of Livers Declined After the Start of Procurement: A Nationwide Organ Procurement Organization Effort

Declining a liver offer during organ procurement likely increases the risk of discard, but the specifics around late reallocation remain obscure. This voluntarily submitted, prospectively collected data describe late declines and the ultimate disposition of 893 livers. Once a liver suffered an intraoperative decline, only 49% of recovered livers were transplanted. Livers declined ≥80 minutes prior to cross-clamp were transplanted 80% of the time versus livers declined ≥80 minutes after cross-clamp, which were transplanted 45% of the time. The final disposition of these livers was into a predetermined backup patient (51%) or required an out-of-sequence expedited allocation (42%). Prerecovery imaging and prerecovery biopsy did not influence the ability to reallocate a liver, and livers from donors after circulatory death are rarely successfully reallocated. In conclusion, this study begins to shed light on this seemingly common practice. A total of 85% of centers had an intraoperative decline, but 4% of centers accounted for 25% of the declines. Organ procurement organizations often enter expedited liver allocation, and instituting a cross-clamp delay to allow for reallocation may influence the disposition of these liver grafts. Expedited allocation was more time consuming than allocation into a predetermined backup. Although a certain number of intraoperative declines probably suggests a healthy amount of donor selection aggressiveness at the time of the initial organ offer, the 47% risk of discard of livers declined intraoperatively suggests that United Network for Organ Sharing should consider systematically collecting data about intraoperative declines so we can learn more about this event that influences organ utilization.

Trends in Outcomes for Marginal Allografts in Liver Transplant

IMPORTANCE

Investigating outcomes after marginal allograft transplant is essential in determining appropriate and more aggressive use of these allografts.

OBJECTIVE

To determine the time trends in the outcomes of marginal liver allografts as defined by 6 different sets of criteria.

DESIGN, SETTING, AND PARTICIPANTS

In this case-control, multicenter study, 75 050 patients who received a liver transplant between March 1, 2002, and September 30, 2016, were retrospectively analyzed to last known follow-up (n = 55 395) or death (n = 19 655) using the United Network for Organ Sharing Database. The study period was divided into three 5-year eras: 2002-2006, 2007-2011, and 2012-2016. Kaplan-Meier survival analysis with log-rank test and Cox proportional hazards regression analysis were used to examine the allograft after transplant with marginal allografts, which were defined as 90th percentile Donor Risk Index allografts (calculated over the entire study period), donor after circulatory death allografts, national share allografts, old age (donors >70 years) allografts, fatty liver allografts, and 90th percentile Discard Risk Index allografts. Statistical analysis was performed from August to December 2019.

MAIN OUTCOMES AND MEASURES

Allograft failure after transplant as defined by the Organ Procurement and Transplantation Network database.

RESULTS

Among the 75 050 patients (44 394 men; mean [SD] age, 54.3 [9.9] years) in the study, Donor Risk Index, patient Model for End-stage Liver Disease scores, and balance of risk scores significantly increased over time. Multivariate Cox proportional hazards regression analysis indicated that 90th percentile Donor Risk Index allograft survival increased across the study period (2002-2006: hazard ratio, 1.41 [95% CI, 1.34-1.49]; 2007-2011: hazard ratio, 1.25 [95% CI, 1.17-1.34]; 2012-2016: hazard ratio, 1.10 [95% CI, 0.98-1.24]). Secondary definitions of marginal allografts (donor after circulatory death, national share, old age donors, fatty liver, and 90th percentile Discard Risk Index) showed similar improvements in allograft survival.

CONCLUSIONS AND RELEVANCE

The study's findings encourage the aggressive use of liver allografts and may indicate a need for a redefinition of allograft marginality in liver transplantation.

Aggressive utilization of liver allografts: Improved outcomes over time

BACKGROUND

Aggressive acceptance of liver allografts has driven utilization of marginal allografts. Our aim was to assess the impact of the aggressive phenotype on transplant center outcomes over time.

METHODS

We used a cohort of 148 361 candidates from the Organ Procurement and Transplantation Network for liver transplantation between 2002 and 2016 in 134 centers. Using the Discard Risk Index, we designated high probability discard allografts by the top 10th percentile for likelihood of discard. Aggressive phenotype was defined by usage of high probability discard (HPD) allografts (top 10th percentile). Our analysis of survival on waitlist and graft survival after transplantation included a comprehensive list of center level covariates across three equal time periods (2002-2006, 2007-2011, and 2012-2016).

RESULTS

After adjusting for recipient and center-level factors, aggressive centers had improving graft survival over time. Aggressive vs non-aggressive centers: 2002-2006 HR 1.12 (1.05-1.19), 2007-2011 HR 1.13 (1.05-1.22), 2012-2016 HR 0.99 (0.89-1.10). Aggressive centers had improved waitlist survival compared with non-aggressive centers after adjusting for allograft disparity.

CONCLUSIONS

Aggressive phenotype had a positive impact on waitlist survival, and graft survival in aggressive centers have improved to benchmark levels over time. These findings serve as justification for aggressive utilization of allografts.

A learning curve in using orphan liver allografts for transplantation

Given the critical shortage of donor livers, marginal liver allografts have potential to increase donor supply. We investigate trends and long-term outcomes of liver transplant using national share allografts transplanted after rejection at the local and regional levels. We studied a cohort of 75 050 candidates listed in the Organ Procurement and Transplantation Network for liver transplantation between 2002 and 2016. We compared patients receiving national share and regional/local share allografts from 2002-2006, 2007-2011, and 2012-2016, performing multivariate Cox regression for graft survival. Recipient and center-level covariates that were not significant (P < .05) were removed. Graft survival of national share allografts improved over time. National share allografts had a 26% increased risk for graft failure in 2002-2006 but no impact on graft survival in 2007-2011 and 2012-2016. The cold ischemia time (CIT) of national share allografts decreased from 10.4 to 8.0 hours. We demonstrate that CIT had significant impact on graft survival using national share allografts (CIT <6 hours: hazard ratio 0.75 and CIT >12 hours: hazard ratio 1.25). Despite a trend toward sicker recipients and poorer quality allografts, graft survival outcomes using national share allografts have improved to benchmark levels. Reduction in cold ischemia time is a possible explanation.

Predictive Capacity of Risk Models in Liver Transplantation

Supplemental Digital Content is available in the text.

Several risk models to predict outcome after liver transplantation (LT) have been developed in the last decade. This study compares the predictive performance of 7 risk models.